This invention relates to an optical fiber coating and to a fiber coding scheme. The invention further relates to a method of coloring an optical fiber coating and to apparatus for coloring an optical fiber coating.
Optical fibers used to connect components in optical assemblies can be as long as 0.8 to 1 meter. Referring now to FIG. 1 of the accompanying drawings, a cross-section of an optical fiber is illustrated. In FIG. 1, the optical fiber 2 consists of an inner core 4 surrounded by a cladding layer 6. The inner core 4 is typically 5 microns in diameter for mono-mode fibers and the cladding layer 6 surrounding the core 4 is typically 60 microns thick. The cladding layer 6 is then coated with first and second acrylic protective coatings 8a, 8b. The first acrylic coating 8a is applied directly to the glass cladding 6. The first acrylic coating 8a is typically 25 to 45 microns thick and is relatively soft so as to not damage the cladding. The second acrylic coating 8b is harder than the first coating has a thickness selected to increase the overall diameter of the optical fiber 2 to around 250 microns.
The core, cladding, and acrylic coatings are typically colorless or transparent which presents considerable difficulty when identifying fiber connections in an optical assembly. Typically, present optical assemblies require 64 or more fiber connections to be identified. Future optical assemblies having more complex optical component arrangements will require even larger numbers of fiber connections.
The number of fibers, and their length increases the complexity and level of difficulty involved with identifying which fiber in a bundle of fibers is to be connected. Forming a series of fiber connections in the correct sequence is a time-consuming task which is prone to human error due to the visual similarity in the fibers.
One known solution to the problems associated with identifying fiber connections is to provide fibers having coloured acrylic coatings. This solution is unsatisfactory as the coloring agents are known to affect the curing process of at least the outer acrylic coating. The limited number of coating colours which can be easily visually distinguished does not greatly improve visual recognition due to the necessity of duplicating fiber colors in an optical assembly having a large number of components. Moreover, the limited number of colors prevents color coatings being established as an identification means in any automated production process. Furthermore, maintaining stocks and the supply of fibers with appropriate color coatings presents inventory problems.
The present invention seeks to obviate or mitigate the above problems by providing a fiber coding scheme which enables an individual fiber to be identified and distinguished from other fibers. The scheme comprises a series of color coded bands which are applied to the ends of optical fibers using a printing process. The color coded banding scheme enables a fiber connection to be uniquely identified.
One object of the invention relates to a fiber coating which identifies the connection to be made by an optical fiber within an optical subassembly.
Another object of the invention relates to an optical fiber coding scheme which codes the optical fiber according to a designated connection the fiber is to form within an optical subassembly.
A first aspect of the invention provides an optical fiber coating including a color sequence, the color sequence comprising a plurality of colored portions along the length of the fiber.
Preferably, the colored portions are dyed. More preferably, the colored portions are dyed by a thermal transfer process.
The color sequence may be selected to identify the fiber uniquely and/or to uniquely identify the connections the fiber is to form.
A second aspect of the invention provides an optical fiber coding scheme comprising the steps of:
selecting a color sequence to identify an optical fiber; and
forming the color sequence along and optical fiber.
Preferably, the color sequence is selected to uniquely identify the connections the optical fiber is to form.
A third aspect of the invention seeks to provide a method of coating an optical fiber with a colored dye, the method comprising the steps of:
positioning a length of the fiber upon a sheet of material coated with a sequence of colored dyes;
heating the fiber using thermal transfer apparatus to transfer such that the colored dye is transferred from the material to the fiber;
cooling the fiber; and
removing the fiber from the thermal transfer apparatus.
Preferably, in the step of positioning a length of fiber, an end portion of the fiber is coated with dye.
A fifth aspect of the invention provides a sheet of material coated with dye for use in a method of dying an optical fiber coating, the dye forming a sequence of differing colors arranged across the sheet.
A sixth aspect of the invention provides a thermal transfer apparatus for use in a method of coating an optical fiber with a sequence of colored dyes, the apparatus including a pair of plates, the plates capable of being pressed together in use. At least one plate may have at least one groove capable of retaining an optical fiber.
A seventh aspect of the invention provides a carrier medium for a dye to be transferred to an optical fiber using thermal transfer apparatus, the carrier medium comprising;
a sheet of material; and
at least one dyed surface area on the sheet of material.
An eighth aspect of the invention provides a carrier medium for a dye to be transferred to an optical fiber, the carrier medium comprising:
a container capable of dispensing a dye solvent onto the optical fiber.
Advantageously, the fiber coating process enables the surface coating of an optical fiber to be colored using a thermal printing process. The printing process mitigates the potential for damage to the optical fiber.
Advantageously, the printing process enables a dye to diffuse into the outer coating of the optical fiber. This ensures that the dye is fixed and provides a means of generating a strong color on the transparent fiber.
Advantageously, by coding the colors of the fiber coating according to the connection the fiber is to make in an optical assembly, achieving the correct sequence of connections is facilitated.